(a) Technical Field
The present disclosure relates to a display device and a method of driving the same. More particularly, the present disclosure relates to an organic light emitting device and a method of driving the same.
(b) Discussion of Related Art
A pixel of an organic light emitting device includes an organic light emitting element, and a thin film transistor (TFT) with a capacitor that drives the same.
The TFT is classified into a polysilicon TFT or an amorphous silicon TFT, according to the kind of active layer that is employed.
Because amorphous silicon is deposited at a low temperature and forms a thin film, the amorphous silicon is generally used for a semiconductor layer of a switching element of a display device that uses a low melting point glass mainly as a substrate. There is a difficulty with the amorphous silicon TFT when increasing an area of a display element, however, due to low electron mobility. Furthermore, because the amorphous silicon TFT continuously applies a DC voltage to the control terminal, a threshold voltage is varied and the amorphous silicon TFT may be thus degraded. This becomes a major factor that shortens the lifetime of the organic light emitting device.
Therefore, application of a polysilicon TFT that has high electron mobility, good high frequency operation characteristics, and a low leakage current is desirable. More specifically, by using a low temperature polycrystalline silicon (LTPS) backplane, the lifetime problem is considerately resolved. A laser shot mark due to laser crystallization, however, causes a deviation in a threshold voltage of the driving transistors within one panel, and thus screen uniformity is deteriorated.
In order to resolve this problem, the organic light emitting device may be provided with a compensation circuit. Such a compensation circuit includes a plurality of TFTs. As the number of TFTs that are included in the compensation circuit increases, the aperture ratio of a pixel is deteriorated, and a burden on a leakage current or a failure of the TFT increases.
A hole type of flat panel display device, such as an organic light emitting device, displays a fixed image for a predetermined time period, for example for one frame, regardless of whether it is a still image or a motion picture. For example, when displaying an object that continuously moves, the object stays at a specific position for one frame and stays at the next position to which the object moves after a time period of one frame at the next frame, and thus motion of the object is discretely displayed. Because a time period of one frame is a time period in which an afterimage is sustained, even if a motion of the object is displayed in this way, the motion of the object appears to be continuous.
When viewing a continuously moving object on a screen, however, because a line of sight of a person continuously moves along a direction of motion of the object, the line of sight of the person collides with a discrete display method of the display device and, thus, a blurring phenomenon occurs. For example, if it is assumed that the display device displays an object that stays at a position A at a first frame and at a position B at a second frame, at the first frame, a line of sight of a person moves from the position A to the position B along an estimated movement path of the object. The object is not actually displayed, however, at an intermediate position between the positions A and B.
Finally, because luminance that is recognized by a person for the first frame is an integrated value of luminance of pixels existing at a path between the positions A and B, that is, an average value between the luminance of an object and the luminance of a background, an object is blurredly viewed.
Because a degree in which an object is blurredly viewed in a hole type display device is proportional to a time period in which the display device sustains the display, a so-called impulse driving method in which an image is displayed only for a partial time period within one frame and a black color is displayed for the remaining time period has been suggested. In such an impulse driving method, however, if unintended light emission occurs for the period during which a black color is displayed, the contrast ratio of an organic light emitting device is reduced.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.